This invention relates to processes which convert paraffins into olefins via dehydrogenation steps and the produced olefins into polyolefins via polymerization steps. The processes are more effective than existing processes and equipment because they integrate more than one process operations into a single process or vessel and utilize recycling of unreacted reactants and products to increase product yield and overall process efficacy and economy. The todays demand for polyolefins, especially polyethylene and polypropylene is high and more effective production methods are in need in terms of reduction in capital and operating expenses. Beyond polyolefins the invention can be applied to production of other polymers from monomers coming out of dehydrogenation reactions. Moreover, the dehydrogenated olefins can be also used in downstream oxidation or synthesis type reactions and reactors for production of specialty chemicals.
Specifically, production of most isotactic, linear polyolefins from C2-C5 monomers such as polypropylene (PP), high density and low density polyethylene (PE), poly-butene-1, poly-4-methylpentene-1, take place with coordination polymerization Also other type of polymers such as polystyrene and polydienes (i.e., poly(1,3-butadiene)) are made by using coordination catalysts and are discussed below as well. Both stirred bed (slurry-liquid phase type) reactors and fluid bed (gas phase using solid supported catalysts) reactors can be employed in coordination polymerization as shown below. Stirred bed reactors to be used can be of a horizontal or vertical vessel type and involve a colloidal catalytic dispersion or a soluble type catalyst, which usually is a coordinated complex (i.e., Ziegler-Natta type catalyst) formed by an organometallic compound (e.g., aluminum alkyl such as dichloroethyl aluminum) with a transition metal salt (e.g., titanium tetrachloride, titanium trichioride) in a hydrocarbon solvent (e.g., hexane, heptane). The so-called Ziegler process for production of high density PE, PP and copolymers of PP-PE (polypropylene-polyethylene) is such process implementation. A modified process (i.e., Philips) requires the use of supported metal oxide catalysts in a similar type of multiphase stirred bed system. Supported catalysts that can be used include chromium, zinc, molybdenum, tin, cobalt, nickel metals on alumina, silica, titania or related supports. Such type of commercially established processes and modifications of these operate at reaction conditions which range from T=50-200° C. and P=1-30 atm.
Gaseous type fluid bed reactors can also carry the coordination polymerization reaction for production of similar structure and density propylene, ethylene, butylene and higher polymers and copolymers. The fluid bed uses only a suspension of catalytic powder of the same metal supported composition and structure as described above in the solution type polymerization processes. Such fluid bed reactor processes operates at moderate pressures (20-30 atm) and temperatures (50-200° C.) and recovers polymer in the form of solid particles under high yields per unit mass of catalyst Since polymerization processes are exothermic the heat of reaction is removed by cooling the reactor externally or internally (by vaporizing a suitable diluent) or by circulating the unreacted gas through external cooling devices.
Experimental results from catalytic permreactors (membrane reactors) for paraffin (e.g., propane, ethane, butane) dehydrogenation reactions have been reported in earlier literature communications. Current implementation of catalytic permreactors and perneators with various permselective wall materials has been also demonstrated in other hydrocarbon processing and upgrading reactions such as in steam and CO2 reforming of metane and natural gas.